Intensity of exposure to pulmonary tuberculosis determines risk of tuberculosis infection and disease

Abstract

Household contacts of pulmonary tuberculosis (TB) patients are at increased risk of TB infection and disease. However, their risk in relation to the intensity of exposure remains unknown.We studied smear-positive TB cases and their household contacts in Vitória, Brazil. We collected clinical, demographic and radiographic information from TB cases, and obtained tuberculin skin test (TST) and QuantiFERON-TB Gold (QFT) results from household contacts. We measured intensity of exposure using a proximity score and sleep location in relation to the TB index case and defined infection by TST ≥10 mm or QFT ≥0.35 UI·mL We ascertained secondary TB cases by reviewing local and nationwide case registries.We included 160 TB index cases and 894 household contacts. 464 (65%) had TB infection and 23 (2.6%) developed TB disease. Risk of TB infection and disease increased with more intense exposures. In an adjusted analysis, the proximity score was associated with TB disease (OR 1.61, 95% CI 1.25-2.08; p<0.000); however, its diagnostic performance was only moderate.Intensity of exposure increased risk of TB infection and disease among household contacts; however, its diagnostic performance was still suboptimal. A biomarker to target preventive therapy is urgently needed in this at-risk population.

Risk factors associated with childhood tuberculosis: a case control study in endemic tuberculosis area

“…This results supports several previous studies in adult TB who stated that more intense exposures are related to higher risk of TB infection. 14,15 Our study showed in multivariate analysis that nutritional status is a factor that influences the incidence of child tuberculosis. It was found that children in the case group had poor nutritional status as much as 68.6% while in the control group only 14.3%.…”

Multiple Exposures, Reinfection, and Risk of Progression to Active Tuberculosis

“…Second, the nature of contacts between infectious and susceptible individuals in this setting may have resulted in a high rate of progression to disease among contacts. Intensity of exposure to an infectious case has been shown to affect the risk of TB infection and disease (18,19). Third, prior exposure to Mycobacterium tuberculosis or prior TB disease may have modified disease risk for individuals with few exposures.…”

Pragmatic tuberculosis prevention policies for primary care in low- and middle-income countries

“…Despite this markedly elevated risk, only a minority (16%) of contacts received preventive treatment, reflecting the low rates of uptake seen globally [2]. Whilst guidelines for preventive treatment in low-and middle-income countries (LMICs) focus principally on children aged <5 years due to the high risk of primary progressive disease and death in this age group, it should be highlighted that in this study 21 (91%) out of 23 of the incident tuberculosis cases occurred in contacts aged ⩾15 years, of whom only 10% received preventive treatment [4].…”

“…In their recent article in the European Respiratory Journal, ACUÑA-VILLAORDUÑA et al [4] demonstrate once again that contacts of patients with tuberculosis are at increased risk of tuberculosis infection and disease. In this study of contacts of any age from a setting with low tuberculosis incidence (38 per 100 000) and HIV prevalence (<1% of the general population), 507 (71%) out of 710 contacts had tuberculosis infection (defined by a positive tuberculin skin test (TST) or interferon-γ release assay (IGRA)).…”

“…Healthcare workers consistently face the triple challenges of insufficient human resources, scarce or inadequate material resources, and a large, heterogeneous population presenting with complex medical and social syndromes. ACUÑA-VILLAORDUÑA et al [4] describe how the absence of clear definitions of contacts at highest risk of tuberculosis prohibits effective implementation of contact investigation and preventive treatment in these settings. As a potential solution, they used an adapted Mandalakas score to predict tuberculosis infection and disease [5].…”